The shipping of goods by truck necessarily includes the loading and unloading of the goods carried thereby. When transporting goods such as bundled building trusses to construction sites it has become common practice to haul the trusses via trucks that are attached to what are known as roll-off trailers.
Roll-off trailers are flatbed trailers that have a plurality of freewheeling rollers disposed along the longitudinal length thereof. The number of rollers varies according to the size of the rollers and the spacing along the trailer bed. Furthermore, there may be more than one row of rollers whose size and spacing may vary.
The use of roll-off trailers eliminates the need for special unloading equipment such as cranes or forklifts that may or may not be at the construction site at the time of delivery of the trusses. Roll-off trailers thus provide flexibility in delivering the trusses at any time.
However, in order to unload the bundled trusses, the truck driver has only several options. One method is to jerk the truck forward to hopefully cause the bundled trusses to roll down the freewheeling rollers and drop onto the ground. This subjects the bundled trusses to a drop of several feet at an uncontrollable speed depending on the suddenness of the jerk. Furthermore, not only do the trusses undergo stress due to the impact with the ground, the trusses bend as they make the transition from roll-off trailer to the ground. Because of this procedure the bundled trusses may become damaged and/or unusable.
Another method for unloading the bundled trusses is to incline the trailer and allow gravity to roll the bundled trusses off the end of the roll-off trailer. This may be accomplished by either driving the truck and roll-off trailer up a grade, or by raising the front end of the roll-off trailer through hydraulic rams or the like. Again, this subjects the bundled trusses to a drop of several feet.
In order to help alleviate the problems associated with the above two methods of unloading the cargo from the roll-off trailers, special tiltable rear ends have been devised. In order to have the bundled trusses roll directly from the roll-off trailer onto the ground without dropping them from a height the end of the roll-off trailer is tiltable. Generally, however, the tilting-bed roll-off trailers utilize a powered winch and cable to control the speed of the cargo. These systems however are not suitable for such cargo as bundled building trusses.
In most cases it is not possible to easily and efficiently control the speed of the trusses as they roll down the length of the roll-off trailer regardless of the unloading method used. Generally, the greater the speed of the trusses, the greater potential for damage to occur. The prior art is thus deficient in the ability to effectively control the unloading of bundled building trusses or other cargo transported by roll-off trailers.
It is thus an object of the present invention to provide a roll-off trailer wherein the speed of the cargo can be controlled during unloading thereof.